1 /*
 2  * Copyright (c) 2018, 2019, Red Hat, Inc. All rights reserved.
 3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 4  *
 5  * This code is free software; you can redistribute it and/or modify it
 6  * under the terms of the GNU General Public License version 2 only, as
 7  * published by the Free Software Foundation.
 8  *
 9  * This code is distributed in the hope that it will be useful, but WITHOUT
10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12  * version 2 for more details (a copy is included in the LICENSE file that
13  * accompanied this code).
14  *
15  * You should have received a copy of the GNU General Public License version
16  * 2 along with this work; if not, write to the Free Software Foundation,
17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18  *
19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20  * or visit www.oracle.com if you need additional information or have any
21  * questions.
22  *
23  */
24 
25 #ifndef SHARE_GC_SHENANDOAH_HEURISTICS_SHENANDOAHPASSIVEHEURISTICS_HPP
26 #define SHARE_GC_SHENANDOAH_HEURISTICS_SHENANDOAHPASSIVEHEURISTICS_HPP
27 
28 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
29 
30 /*
31  * The passive heuristic is for use only with the passive mode. In
32  * the passive mode, Shenandoah only performs STW (i.e., degenerated)
33  * collections. All the barriers are disabled and there are no concurrent
34  * activities. Therefore, this heuristic _never_ triggers a cycle. It
35  * will select regions for evacuation based on ShenandoahEvacReserve,
36  * ShenandoahEvacWaste and ShenandoahGarbageThreshold. Note that it does
37  * not attempt to evacuate regions with more garbage.
38  */
39 class ShenandoahPassiveHeuristics : public ShenandoahHeuristics {
40 public:
41   ShenandoahPassiveHeuristics(ShenandoahSpaceInfo* space_info);
42 
43   virtual bool should_start_gc();
44 
45   virtual bool should_unload_classes();
46 
47   virtual bool should_degenerate_cycle();
48 
49   virtual void choose_collection_set_from_regiondata(ShenandoahCollectionSet* set,
50                                                      RegionData* data, size_t data_size,
51                                                      size_t free);
52 
53   virtual const char* name()     { return "Passive"; }
54   virtual bool is_diagnostic()   { return true; }
55   virtual bool is_experimental() { return false; }
56 };
57 
58 #endif // SHARE_GC_SHENANDOAH_HEURISTICS_SHENANDOAHPASSIVEHEURISTICS_HPP